The present invention relates to the field of communications, and, more particularly, to phased array antennas and related methods.
Antenna systems are widely used in both ground based applications (e.g., cellular antennas) and airborne applications (e.g., airplane or satellite antennas). For example, so-called xe2x80x9csmartxe2x80x9d antenna systems, such as adaptive or phased array antennas, combine the outputs of multiple antenna elements with signal processing capabilities to transmit and/or receive communications signals (e.g., microwave signals, RF signals, etc.). As a result, such antenna systems can vary the transmission or reception pattern (i.e., xe2x80x9cbeam shapingxe2x80x9d or xe2x80x9cspoilingxe2x80x9d) or direction (i.e., xe2x80x9cbeam steeringxe2x80x9d) of the communications signals in response to the signal environment to improve performance characteristics.
A typical phased array antenna may include, for example, one or more element controllers connected to a central controller. Among other functions, the element controllers process beam control commands generated by the central controller (e.g., beam steering signals and/or beam spoiling signals) and provide output control signals for each of the phased array antenna elements. More particularly, each antenna element may have a phase shifter, attenuator, delay generator, etc., and the output control signals from the element controller may be used to control a phase, attenuation, or delay thereof. Thus, the transmission or reception pattern may be varied, as noted above.
In such phased array antennas, it is quite often necessary to perform compensation for one or more varying control parameters. For example, temperature changes may have a significant impact on phase shifters, attenuators, or operating frequencies of the phased array antenna. This, in turn, may result in undesirable signal characteristics if proper compensation is not performed.
Two different prior art approaches are typically used to perform temperature compensation in phased array antennas. The first approach is to store temperature compensation look-up tables at each element controller. Each element controller then manages the temperature compensation for its associated antenna elements at all possible operating temperatures.
An example of a phased array antenna which utilizes element controller look-up tables is disclosed in U.S. Pat. No. 5,283,587 to Hirshfield et al. entitled xe2x80x9cActive Transmit Phased Array Antenna.xe2x80x9d In this phased array antenna, a microprocessor element controller is used to control a group of antenna elements within the phased array antenna. The microprocessor element controller generates control voltages for controlling phase shifters and attenutators for the antenna elements. Further, because of potential temperature changes, a thermistor may be included to compensate the control voltages. The look-up tables are stored by the microprocessor element controller and are used to allow linearization of the control voltages.
One drawback of the above prior art approach is that the possible range of operating temperatures can often be quite large for a phased array antenna. For example, the operating temperature range of a phased array antenna on a satellite can vary quite widely depending upon whether the antenna is in sunlight or not. As a result, to implement the above prior art approach the element controllers will have to store a rather large set of compensation data to accommodate the entire possible operating temperature range. Thus, larger memory and addressing circuitry may be required in each element controller, which in turn may increase costs, space requirements, and power consumption.
The second prior art approach is to have the central controller perform essentially all of the temperature compensation and beam steering/spoiling processing. That is, each time the central processor sends new beam steering/spoiling commands to a particular element controller or implements a new operating frequency, the central controller also has to provide the appropriate temperature compensation. Yet, even though control parameters such as temperature may vary relatively slowly, other parameters such as frequency, for example, may vary relatively quickly. This is particularly true in phased array antennas which implement frequency hopping, for example. As such, this prior art approach may result in significant bandwidth limitations, particularly for antennas with large arrays and that have relatively fast frequency hopping or beam steering requirements.
In view of the foregoing background, it is therefore an object of the present invention to provide a phased array antenna having efficient compensation data distribution and related methods.
This and other objects, features, and advantages in accordance with the present invention are provided by a phased array antenna which may include a substrate and at least one phased array antenna element carried thereby, at least one element controller for controlling the at least one phased array antenna element based upon desired compensation data, and a central controller for supplying to the at least one element controller a current value of a quick control parameter and a block of current compensation data. The block of current compensation data may be based upon a current value of a slow control parameter and a range of possible values for the quick control parameter. Further, the quick control parameter may vary more quickly than the slow control parameter. Additionally, the at least one element controller may determine the desired compensation data based upon the supplied block of current compensation data and the current value of the quick control parameter.
More particularly, the central controller may supply the block of current compensation data to the at least one element controller based upon a change of the current value of the slow control parameter, and within a predetermined time thereof. Similarly, the central controller may supply the current value of the quick control parameter to the at least one element controller based upon a change in the quick control parameter, and also within a predetermined time thereof. Additionally, the central controller may supply the current value of the quick control parameter to the at least one element controller on a periodic basis.
Furthermore, the quick control parameter may be operating frequency, phase, and/or attenuation, and the slow control parameter may be temperature and/or beam shape, for example. Also, the at least one element controller may include a memory for storing the block of current compensation data. Plus, the central controller may generate beam control commands, and the at least one element controller may additionally include a processor for cooperating with the memory for controlling the at least one phased array antenna element based upon the beam control commands and the desired compensation data.
A method aspect of the invention is for using an element controller, such as the one described above, in a phased array antenna. The method may include supplying to the element controller a current value of a quick control parameter and a block of current compensation data. The block of current compensation data may be based upon a current value of a slow control parameter and a range of possible values for the quick control parameter. Further, the quick control parameter may vary more quickly than the slow control parameter. Additionally, the method may also include, at the element controller, determining desired compensation data based upon the supplied block of current compensation data and the current value of the quick control parameter.